The present invention relates generally to optical recording media and a method of producing the same, and more particularly, to an optical recording medium capable of having data printed on a label side opposite to a light incident side and a method of producing the same.
As recording media for recording large digital data, optical recording media represented by CDs (Compact Discs) and DVDs (Digital Versatile Discs) have widely been used and particularly optical recording media of such a type that data can be recorded by users are rapidly diffusing in recent years. As optical recording media capable of recording data are usable for preserving digital data such as image data and musical data having larger files simply at low cost, they have become utilized by a great deal of users. With the diffusion of optical recording media of the type mentioned above, there has increasingly developed a demand for making original optical recording media by having data printed on label sides opposite to light incident sides with printers and optical recording media capable of satisfying such a demand have already been developed and marketed.
An ink receiving layer for fixing ink is provided on the label side of an optical recording medium, so that printing can be done on the label side by using an ink-jet printer for supplying ink to the ink receiving layer.
However, printing quality for the optical recording medium is generally lower than what is for glossy paper and the problem is that the performance of the ink-jet printer capable of high-quality printing cannot be brought out satisfactorily. In order to solve this problem, there has been proposed an optical recording medium by JP-A-2002-237103 in which the surface roughness of an ink receiving layer is restrained from exceeding a predetermined value.
Although it is considered desirable to form such an ink receiving layer by using a spin coating method to reduce the surface roughness of the ink receiving layer, the surface roughness of the ink receiving layer thus formed is not always reducible even when an application liquid for making obtainable a flat smooth surface is selected because the surface roughness of the ink receiving layer is affected by the undercoat thereof and the problem is that high printing quality remains unavailable in this case.
Consequently, it has been not necessarily easy to reduce the surface roughness even in case that the ink receiving layer is formed by using the spin coating method.
On the other hand, there is a slit coating method known as a coating method capable of forming a coating film having a flat smooth surface and normally used for a rectangular shaped object (e.g., display panel) to be processed (refer to JP-A-11-162808 and JP-A-2000-167476). When the slit coating method is employed for disc-shaped objects to be processed like general optical recording media, the coating method brings with it a number of difficulties including causing a great step (difference in level) at the joint portion.
With the great step existing on the ink receiving layer, the step becomes conspicuous when printing is done with a printer, which poses a serious problem in that printing quality is deteriorated.